Rotor blade root assembly for a wind turbine

ABSTRACT

A root assembly for a rotor blade of a wind turbine includes a blade root section having an inner sidewall surface and an outer sidewall surface separated by a radial gap, a plurality of root inserts spaced circumferentially within the radial gap, and a plurality of spacers configured between one or more of the root inserts. Further, each of the root inserts includes at least one bore hole surrounded by a pre-cured or pre-consolidated composite material. In addition, the pultruded spacers are constructed of a pre-cured or pre-consolidated composite material.

FIELD OF THE INVENTION

The present subject matter relates generally to wind turbines and, moreparticularly, to a rotor blade root assembly for a wind turbine.

BACKGROUND OF THE INVENTION

Wind power is considered one of the cleanest, most environmentallyfriendly energy sources presently available, and wind turbines havegained increased attention in this regard. A modern wind turbinetypically includes a tower, a generator, a gearbox, a nacelle, and arotor. The rotor is coupled to the nacelle and includes a rotatable hubhaving one or more rotor blades. The rotor blades are connected to thehub by a blade root. The rotor blades capture kinetic energy from windusing known airfoil principles and convert the kinetic energy intomechanical energy through rotational energy to turn a shaft coupling therotor blades to a gearbox, or if a gearbox is not used, directly to thegenerator. The generator then converts the mechanical energy toelectrical energy that may be deployed to a utility grid.

The particular size of the rotor blades is a significant factorcontributing to the overall capacity of the wind turbine. Specifically,increases in the length or span of a rotor blade may generally lead toan overall increase in the energy production of a wind turbine.Accordingly, efforts to increase the size of rotor blades aid in thecontinuing growth of wind turbine technology and the adoption of windenergy as an alternative and commercially competitive energy source.Such increases in rotor blade size, however, may impose increased loadson various wind turbine components. For example, larger rotor blades mayexperience increased stresses at the connection between the blade rootand the hub, leading to challenging design constraints, bothcharacterized by extreme events and fatigue life requirements.

Many rotor blades utilize root bolt inserts to reduce the stresses atthe blade root-hub interface. Such root bolt inserts can be producedusing a variety of processes, including but not limited to pultrusions.A common approach is to infuse root bolt inserts with fabrics androvings to provide a laminate substrate by which later infusions can beused to effectively bond the insert into the blade root laminates.Round, square, trapezoidal, or similar profiles may be used, though thenumber of root bolt inserts required often leaves a gap between insertsthat must be filled with a mixture of glass and resin. This processentails cutting very small strips of glass and placing the stripsmanually in the blade root and then using a typical vacuum infusionprocess. Such a process can be labor-intensive and often results in poorlaminate quality of the laminates between the root bolt inserts.

Thus, there is a need for an improved rotor blade root assembly thataddresses the aforementioned issues. Accordingly, a rotor blade rootassembly that reduces labor cycle time and improves laminate qualitywould be advantageous.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In accordance with one embodiment of the invention, a root assembly fora rotor blade of a wind turbine is disclosed. The root assembly includesa blade root section and a plurality of root inserts. The blade rootsection has an inner sidewall surface and an outer sidewall surfaceseparated by a radial gap. Further, the blade root section isconstructed of a first composite material. More specifically, the firstcomposite material includes a thermoplastic material or a thermosetmaterial. The root inserts are spaced circumferentially within theradial gap. Further, each of the root inserts includes at least one borehole surrounded by a second composite material. The second compositematerial includes a thermoplastic material or a thermoset material;however, the second composite material is different than the firstcomposite material. In other words, the resin system of the blade rootsection is the opposite of the root inserts. In addition, each of thebore holes is configured to receive a root bolt that secures the rootassembly to a hub of the wind turbine.

More specifically, in one embodiment, the first composite material mayinclude the thermoset material, whereas the second composite materialmay include the thermoplastic material. Alternatively, in anotherembodiment, the first composite material may include the thermoplasticmaterial, whereas the second composite material may include thethermoset material.

In further embodiments, the thermoplastic material may include at leastone of polyvinyl chlorides (PVC), polyvinylidene chlorides, polyvinylacetates, polypropylenes, polyethylenes, polystyrenes, polyurethanes,polyphenyl sulfide, polybutylene terephthalate (PBT), polyamides,polymethyl methacrylate (PMMA), polyethylene terephthalate (PET),glycolised polyethylene terephthalate (PET-G), or similar. In additionalembodiments, the thermoset material may include at least one ofpolyester, ester, epoxy, melamine formaldehyde, urea formaldehyde, orsimilar.

In yet another embodiment, the root assembly may also include aplurality of spacers configured between one or more of the root inserts.More specifically, each of the spacers may be constructed of a pre-curedor pre-consolidated composite material, e.g. a thermoplastic material orthermoset material as described herein.

In addition, in certain embodiments, the thermoset material and/or thethermoplastic material described herein may be reinforced with one ormore fibers. For example, the fiber(s) may include carbon fibers, carbonrovings, glass fibers, or glass rovings, or similar.

Further, in additional embodiments, the root assembly may furtherinclude a bonding agent configured within the radial gap. Morespecifically, in certain embodiments, the bonding agent may includechopped fiber mat (CFM), a biaxially-stretched plastic film, athree-dimensional glass fabric, or similar.

In further embodiments, the root assembly may be formed via at least oneof welding, vacuum infusion, resin transfer molding (RTM), light resintransfer molding (RTM), vacuum assisted resin transfer molding (VARTM),or similar.

In another aspect, the present disclosure is directed to a root assemblyfor a rotor blade of a wind turbine. The root assembly includes a bladeroot section and a plurality of root inserts. The blade root sectionincludes an inner sidewall surface and an outer sidewall surface. Theinner and outer sidewall surfaces are separated by a radial gap.Further, the blade root section is constructed, at least in part, of athermoplastic material. The root inserts are spaced circumferentiallywithin the radial gap. In addition, each of the root inserts includes atleast one bore hole surrounded by a thermoplastic material. Further,each of the bore holes is configured to receive a root bolt to securethe root assembly to a hub of the wind turbine. It should be understoodthat the root assembly may be further configured with any of theadditional features as described herein.

In yet another aspect, the present disclosure is directed to a rootassembly for a rotor blade of a wind turbine. The root assembly includesa blade root section and a plurality of root inserts. The blade rootsection includes an inner sidewall surface and an outer sidewallsurface. The inner and outer sidewall surfaces re separated by a radialgap. Further, the blade root section is constructed of at least onethermoset material and at least one thermoset material. The root insertsare spaced circumferentially within the radial gap. In addition, each ofthe root inserts includes at least one bore hole surrounded by athermoset material or a thermoplastic material. Further, each of thebore holes is configured to receive a root bolt to secure the rootassembly to a hub of the wind turbine. It should be understood that theroot assembly may be further configured with any of the additionalfeatures as described herein.

These and other features, aspects and advantages of the presentinvention will be further supported and described with reference to thefollowing description and appended claims. The accompanying drawings,which are incorporated in and constitute a part of this specification,illustrate embodiments of the invention and, together with thedescription, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 illustrates a perspective view of one embodiment of a windturbine according to the present disclosure;

FIG. 2 illustrates a perspective view of one embodiment of a rotor bladeof a wind turbine according to the present disclosure;

FIG. 3 illustrates an enlarged view of one embodiment of an end face ofa root assembly of a rotor blade according to the present invention;

FIG. 4 illustrates an enlarged view of another embodiment of an end faceof a root assembly of a rotor blade according to the present invention;

FIG. 5 illustrates an enlarged view of yet another embodiment of an endface of a root assembly of a rotor blade according to the presentinvention;

FIG. 6 illustrates a detailed view of a portion of a root assembly of awind turbine rotor blade according to the present disclosure;

FIG. 7 illustrates a perspective view of one embodiment of a root insertfor a root assembly of a wind turbine rotor blade according to thepresent disclosure;

FIG. 8 illustrates a perspective view of one embodiment of a spacer fora root assembly of a wind turbine rotor blade according to the presentdisclosure;

FIG. 9 illustrates a cross-sectional view of the spacer of FIG. 6 alongline 7-7;

FIG. 10 illustrates a perspective view of a portion of a root assemblyof a wind turbine rotor blade according to the present disclosure;

FIG. 11 illustrates an enlarged view of another embodiment of a portionof a root assembly of a wind turbine rotor blade according to thepresent invention;

FIG. 12 illustrates a detailed view of a portion of a root assembly of awind turbine rotor blade according to the present disclosure;

FIG. 13 illustrates a perspective view of another embodiment of a rootinsert for a root assembly of a wind turbine rotor blade according tothe present disclosure;

FIG. 14 illustrates a flow diagram of a method for manufacturing a rootassembly for a wind turbine rotor blade according to the presentdisclosure;

FIG. 15 illustrates a perspective view of a shell mold used during themanufacturing process of the root assembly of a wind turbine rotor bladeaccording to the present disclosure, particularly illustrating the outerlayer placed onto the shell mold;

FIG. 16 illustrates a perspective view of a shell mold used during themanufacturing process of the root assembly of a wind turbine rotor bladeaccording to the present disclosure, particularly illustrating the outerlayer, the root inserts, and the spacers placed onto the shell mold;

FIG. 17 illustrates a perspective view of a shell mold used during themanufacturing process of the root assembly of a wind turbine rotor bladeaccording to the present disclosure, particularly illustrating the rootinserts and the spacers secured in the shell mold via a removableflange; and

FIG. 18 illustrates a perspective view of a shell mold used during themanufacturing process of the root assembly of a wind turbine rotor bladeaccording to the present disclosure, particularly illustrating the rootinserts and the spacers between the inner and outer layers of compositematerial before infusion.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

Generally, the present disclosure is directed to a root assembly for arotor blade of a wind turbine and methods of manufacturing same. Theroot assembly includes a blade root section having an inner sidewallsurface and an outer sidewall surface separated by a radial gap, aplurality of root inserts spaced circumferentially within the radialgap, and optionally a plurality of spacers configured between one ormore of the root inserts. Further, the blade root section may beconstructed, at least in part, from a thermoplastic material or athermoset material. In addition, each of the root inserts includes atleast one bore hole surrounded by a pre-cured or pre-consolidatedcomposite material, e.g. a thermoplastic material or a thermosetmaterial. Moreover, the spacers may also be constructed of a pre-curedor pre-consolidated composite material, e.g. a thermoplastic material ora thermoset material. More specifically, the thermoplastic and/orthermoset materials may be reinforced with glass or carbon fibers orrovings.

The present disclosure provides many advantages not present in the priorart. For example, the root assembly of the present disclosure providesimproved laminate quality between the root inserts, e.g. due to thecombination of thermoset and/or thermoplastic components. In addition,the root assembly of the present disclosure enables the use of rootinserts in thermoplastic as well as thermoset rotor blades. Further, theresin consumption in the primary shell infusion process of the rotorblades may be reduced, thereby reducing overall manufacturing costs.Further, the labor required to place the root inserts and/or the spacersinto the shell mold may be reduced as compared to using dry fabrics tofill the volume. Moreover, the pultruded root inserts allow forsignificant reductions in manufacturing cycle time as compared to usingT-bolt and/or barrel nut configurations.

Referring now to the drawings, FIG. 1 illustrates a perspective view ofa horizontal axis wind turbine 10. It should be appreciated that thewind turbine 10 may also be a vertical-axis wind turbine. As shown inthe illustrated embodiment, the wind turbine 10 includes a tower 12, anacelle 14 mounted on the tower 12, and a rotor hub 18 that is coupledto the nacelle 14. The tower 12 may be fabricated from tubular steel orother suitable material. The rotor hub 18 includes one or more rotorblades 16 coupled to and extending radially outward from the hub 18. Asshown, the rotor hub 18 includes three rotor blades 16. However, in analternative embodiment, the rotor hub 18 may include more or less thanthree rotor blades 16. The rotor blades 16 rotate the rotor hub 18 toenable kinetic energy to be transferred from the wind into usablemechanical energy, and subsequently, electrical energy. Specifically,the hub 18 may be rotatably coupled to an electric generator (notillustrated) positioned within the nacelle 14 for production ofelectrical energy.

Referring to FIG. 2, one of the rotor blades 16 of FIG. 1 is illustratedin accordance with aspects of the present subject matter. As shown, therotor blade 16 generally includes a root assembly 30 having a blade rootsection 32 that is configured to be mounted or otherwise secured to thehub 18 (FIG. 1) of the wind turbine 10. In addition, a blade tip section34 is disposed opposite the blade root section 32. A body shell 21 ofthe rotor blade generally extends between the blade root section 32 andthe blade tip section 34 along a longitudinal axis 24. The body shell 21may generally serve as the outer casing/covering of the rotor blade 16and may define a substantially aerodynamic profile, such as by defininga symmetrical or cambered airfoil-shaped cross-section. The body shell21 may also define a pressure side 36 and a suction side 38 extendingbetween leading and trailing ends 26, 28 of the rotor blade 16. Further,the rotor blade 16 may also have a span 23 defining the total lengthbetween the blade root section 32 and the blade tip section 34 and achord 25 defining the total length between the leading edge 26 and thetrailing edge 28. As is generally understood, the chord 25 may generallyvary in length with respect to the span 23 as the rotor blade 16 extendsfrom the blade root section 32 to the blade tip section 34.

In several embodiments, the body shell 21 of the rotor blade 16 may beformed as a single, unitary component. Alternatively, the body shell 21may be formed from a plurality of shell components or segments.Additionally, the body shell 21 may generally be formed from anysuitable material. For instance, in one embodiment, the body shell 21may be formed entirely from a laminate composite material, such as acarbon fiber reinforced laminate composite or a glass fiber reinforcedlaminate composite. Alternatively, one or more portions of the bodyshell 21 may be configured as a layered construction and may include acore material, formed from a lightweight material such as wood (e.g.,balsa), foam (e.g., extruded polystyrene foam) or a combination of suchmaterials, disposed between layers of laminate composite material.

The rotor blade 16 may also include one or more longitudinally extendingstructural components configured to provide increased stiffness,buckling resistance and/or strength to the rotor blade 16. For example,the rotor blade 16 may include a pair of longitudinally extending sparcaps 20 configured to be engaged against the opposing inner surfaces ofthe pressure and suction sides 36, 38 of the rotor blade 16,respectively. Additionally, one or more shear webs (not shown) may bedisposed between the spar caps 20 so as to form a beam-likeconfiguration. The spar caps 20 may generally be designed to control thebending stresses and/or other loads acting on the rotor blade 16 in agenerally span-wise direction (a direction parallel to the span 23 ofthe rotor blade 16) during operation of a wind turbine 10. Similarly,the spar caps 20 may also be designed to withstand the span-wisecompression occurring during operation of the wind turbine 10.

Referring now to FIGS. 3-13 various views and/or components of multipleembodiments of the root assembly 30 according to the present disclosureare illustrated. More specifically, as shown, the root assembly 30includes a blade root section 32 having an end face 33 with asubstantially annular cross-section defined by an inner sidewall surface40 and an outer sidewall surface 42. Further, as shown generally in thefigures, the inner and outer sidewall surfaces 40, 42 are separated by aradial gap 44. In addition, in certain embodiments, the blade rootsection 32 may be constructed of a first composite material. Forexample, in certain embodiments, the first composite material mayinclude a thermoplastic material or a thermoset material. In addition,the thermoset or thermoplastic materials of the blade root section 32may be reinforced with one or more fibers, including but not limited toglass or carbon fibers or rovings.

In addition, as shown, the root assembly 30 also includes a plurality ofroot inserts 46 spaced circumferentially within the radial gap 44 andoptionally a plurality of spacers 52 (FIGS. 4-6 and 8-13) configuredbetween one or more of the root inserts 46. Moreover, each of the rootinserts 46 includes at least one bore hole or bushing 48 surrounded by asecond composite material 50. For example, as shown in FIGS. 3 and 4,each of the root inserts 46 includes a single bushing 48 surrounded bythe second composite material 50. Alternatively, as shown in FIG. 5, oneor more of the root inserts 46 may include a plurality of bushings 48surrounded by a second composite material 50. More specifically, incertain embodiments, the bushing(s) 48 may include a metal bushing curedwithin and surrounded by the second composite material 50. For example,in certain embodiments, the second composite material (like the firstcomposite material) may include a thermoplastic material or a thermosetmaterial. In addition, as mentioned, the thermoset or thermoplasticmaterials may be reinforced with one or more fibers, including but notlimited to glass or carbon fibers or rovings.

More specifically, in certain embodiments, the second composite materialmay be different than the first composite material. For example, thefirst composite material may be a thermoset material, whereas the secondcomposite material may be a thermoplastic material. In alternativeembodiments, the first composite material may be a thermoplasticmaterial, whereas the second composite material may be a thermosetmaterial. In still additional embodiments, both the first and secondcomposite materials may be thermoplastic materials. In addition, thespacers 52 as described herein may be constructed, at least in part, ofa pre-cured or pre-consolidated composite material 54, e.g. athermoplastic material or a thermoset material.

The thermoplastic materials as described herein generally encompass aplastic material or polymer that is reversible in nature. For example,thermoplastic materials typically become pliable or moldable when heatedto a certain temperature and solidify upon cooling. Further,thermoplastic materials may include amorphous thermoplastic materialsand semi-crystalline thermoplastic materials. For example, someamorphous thermoplastic materials may generally include, but are notlimited to styrenes, vinyls, cellulosics, polyesters, acrylics,polysulphones, and/or imides. More specifically, example amorphousthermoplastic materials may include polystyrene, acrylonitrile butadienestyrene (ABS), polymethyl methacrylate (PMMA), glycolised polyethyleneterephthalate (PET-G), polycarbonate, polyvinyl acetate, amorphouspolyamide, polyvinyl chlorides (PVC), polyvinylidene chloride,polyurethane, or similar. In addition, example semi-crystallinethermoplastic materials may generally include, but are not limited topolyolefins, polyamides, fluropolymer, ethyl-methyl acrylate,polyesters, polycarbonates, and/or acetals. More specifically, examplesemi-crystalline thermoplastic materials may include polybutyleneterephthalate (PBT), polyethylene terephthalate (PET), polypropylene,polyphenyl sulfide, polyethylene, polyamide (nylon), polyetherketone, orsimilar. Further, the thermoset materials as described herein generallyencompass a plastic material or polymer that is non-reversible innature. For example, thermoset materials, once cured, cannot be easilyremolded or returned to a liquid state. As such, after initial forming,thermoset materials are generally resistant to heat, corrosion, and/orcreep. Example thermoset materials may generally include, but are notlimited to, some polyesters, some polyurethanes, esters, epoxies,melamine formaldehyde, urea formaldehyde, or similar.

In addition, in certain embodiments, the root inserts 46 and/or thespacers 52 may be pultruded from one or more composite materials,respectively. As used herein, the terms “pultruded,” “pultrusions,” orsimilar generally encompass reinforced materials (e.g. fibers or wovenor braided strands) that are impregnated with a resin and pulled througha stationary die such that the resin cures or undergoes polymerization.As such, the process of manufacturing pultruded members is typicallycharacterized by a continuous process of composite materials thatproduces composite parts having a constant cross-section. Thus, thecomposite materials may include pultrusions constructed of glass orcarbon reinforced thermoset or thermoplastic materials. Further, theroot inserts 46 and/or the spacers 52 may be formed of the samecomposite materials or different composite materials. In addition, thepultruded components may be produced from rovings, which generallyencompass long and narrow bundles of fibers that are not combined untiljoined by a cured resin.

In particular embodiments, as shown in FIGS. 8 and 9, the spacers 52 mayalso include a core material 58. For example, in certain embodiments,the core material 58 may include a lightweight material such as wood(e.g., balsa), foam (e.g., extruded polystyrene foam) or a combinationof such materials. More specifically, the core material 58 may include alow-density foam material. As such, the core material 58 is configuredto occupy space that would otherwise fill with fiber material and/orresin during the pultrusion process. Thus, in certain embodiments, thecore material 58 may be configured to fill enough space in thepultrusion spacer to allow sufficient curing throughout the spacer 52.

Referring particularly to FIGS. 6-10, the root inserts 46 and/or thespacers 52 may each include side edges 45, 53, respectively, such thatwhen the root inserts 46 and the spacers 52 are arranged in the rootassembly 30 (FIGS. 6 and 10), the side edges 45, 53 substantially alignand are flush to form first and second continuous surfaces 55, 57. Morespecifically, the plurality of root inserts 46 may include any suitablecross-sectional shape 60. For example, as shown in FIGS. 5-8, thecross-sectional shape 60 of the root inserts 46 may be a square, arectangle, a circle, or similar. More specifically, as shown in FIGS.4-10, the cross-sectional shape 60 of the root inserts 46 aresubstantially square. Alternatively, as shown in FIGS. 11-13, thecross-sectional shape 60 of the root inserts 46 is substantiallycircular. In additional embodiments, the plurality of spacers 52 mayalso include any suitable cross-sectional shape 62. For example, asshown in FIGS. 4-10, the cross-sectional shape 62 of the spacers maycorrespond to the cross-sectional shape 60 of the plurality of rootinserts 46 such that the inserts and spacers may be aligned together inthe radial gap 44. In addition, the root inserts 46 and spacers 52 maybe sized so as to follow the curvature of the radial gap 44.Alternatively, as shown in FIGS. 11-13, the cross-sectional shape 62 ofthe spacers 52 may include a generally hour glass shape that correspondsto the circular cross-sectional shape 60 of the root inserts 46. Forexample, as shown in the illustrated embodiment, the side edges 53 ofthe spacers 52 may be concave such that the edges receive the rootinserts 46 therein.

In additional embodiments, as shown in FIG. 6, the root assembly 30 mayalso include a bonding agent 64 configured within the radial gap 44,e.g. between the various surfaces between the root inserts 46 and/orspacers 52. Thus, the bonding agent 64 is configured to promote surfaceadhesion and/or resin transfer throughout the root assembly 30 duringthe manufacturing process. More specifically, in particular embodiments,the bonding agent 64 may include chopped fiber mat (CFM), abiaxially-stretched plastic film, a three-dimensional glass fabric, orsimilar. Thus, in additional embodiments, the root assembly 30 may beformed via at least one of vacuum infusion, resin transfer molding(RTM), light resin transfer molding (RTM), vacuum assisted resintransfer molding (VARTM), or similar, which is discussed in more detailbelow.

Referring now to FIG. 14, a flow diagram of one embodiment of a method100 of manufacturing a root assembly 30 for a rotor blade 16 of a windturbine 10 is illustrated. As shown at 102, the method 100 includesplacing an outer layer 42 of composite material into a shell mold 66 ofa blade root section 32 of the rotor blade 16 to form an outer sidewallsurface 42 of the root assembly 30, for example, as shown in FIG. 15.More specifically, the outer layer 42 of composite material may includea thermoplastic material skin that may optionally be reinforced withglass or carbon fibers. Thus, the method 100 may including laying downone or more plies (e.g. glass or carbon fibers) in the shell mold 66that extend from the end face 33 of the blade root section 32 toward theblade tip section 34. In addition, the plies are typically laid up inthe mold so as to extend from the leading edge 26 to the trailing edge28 of the rotor blade 16. The plies may then be infused together, e.g.via a thermoplastic material. Further, as shown, the shell mold 66 mayinclude a first shell half 68 and a second shell half (not shown). Assuch, the method 100 may include forming a first blade section via thefirst shell half 68, forming a second blade section via the second shellhalf, and bonding the first and second blade sections together, e.g. viaan adhesive. It should be understood that each blade section may beformed via the method steps as described herein.

Thus, as shown at 104, the method 100 may also include placing aplurality of root inserts 46 atop the outer layer 42, for example, asshown in FIG. 16. In particular embodiments, as shown in FIG. 17, eachroot insert 46 may be placed in the mold and then bolted to a removableflange 70 which can be removed at a later time. As mentioned, the rootinserts 46 may be constructed of a thermoplastic or a thermosetmaterial. In addition, as shown at 106, the method 100 may optionallyinclude placing a plurality of spacers 52 between one or more of theplurality of root inserts 46, for example, as shown in FIG. 16. Itshould be understood that the spacers 52 may be placed into the shellmold simultaneously with the root inserts 46, e.g. by alternativelyplacing a spacer 52, then an insert 46, and so on. For example, incertain embodiments, the method 100 may include placing at least onespacer 52 adjacent to an installed insert 46 and then subsequentlyplacing another spacer 52 on the other side of the installed insert 46and bolting the spacers 52 to the removable flange 70. In other words,the step of placing the plurality of root inserts 46 atop the outerlayer 42 and placing the plurality of spacers 52 between one or more ofthe plurality of root inserts 46 may include mounting the root inserts46 and/or the spacers 52 to the removable flange 70, which is configuredto maintain the position of the root inserts 46 and/or the spacers 52during infusing. For example, as shown, the root inserts 46 and thespacers 52 may be mounted to the removable flange via one or morefasteners 72.

It should also be understood that any arrangement of rootinserts-to-spacers may be used in the root assembly 30. For example, incertain embodiments, the root assembly 30 may include only root inserts46 as shown in FIG. 3. Alternatively, the method 100 of assembling theroot assembly 30 may include varying a number of the root inserts 46 andspacers 52 based on load concentrations in the root assembly 30. Morespecifically, the arrangement of root inserts-to-spacers can be tailoredsuch that the number of root inserts 46 is increased in areas of higherconcentrations of load (for example, the portion of the root closest tothe spar caps 20). As such, in certain embodiments, the number of rootinserts 46 may be increased or decreased based on varying loadconcentrations in the root assembly 30. In a further embodiment, asshown in FIGS. 4, 11, and 16, the method 100 may include placing atleast one spacer 52 between each of the root inserts 46 such that theroot inserts 46 are evenly spaced. Such an embodiment provides equalseparation of the inserts 46 to tailor the rotor blade 16 to the minimumnumber of bolts required without having to over design the blade rootdue to standard geometry of the insert 46. Alternatively, as shown inFIG. 5, the method 100 may include placing the spacers 52 between theroot inserts 46 randomly.

In further embodiments, the method 100 may also include preparing one ormore surfaces 45, 53 of the root inserts 46 and/or the spacers 52 (orthe inner and outer sidewall surfaces 40, 42) so as to improve adhesionof the surfaces during infusion and/or to promote resin transfer duringinfusing. For example, in certain embodiments, the step of preparing oneor more surfaces may include providing a bonding agent 64 between one ormore of the surfaces, grinding one or more of the surfaces, or similar.

In addition, as mentioned, the method 100 may also include forming theroot inserts 46 and/or the spacers 52 using any suitable manufacturingprocesses. For example, in certain embodiments, the method 100 mayinclude pultruding the root inserts 46 and/or the spacers 52, e.g. usingthermoplastic or thermoset materials reinforced with carbon or glassfibers. More specifically, in particular embodiments, the step ofpultruding the spacers 52 may further include providing a low-densitycore material 58 to fill an internal volume of the spacers 52.

Referring still to FIG. 14, as shown at 108, the method 100 may alsoinclude placing an inner layer 40 of composite material into the shellmold 66 atop the root inserts 46 and the spacers 52 to form an innersidewall surface 40 of the root assembly 30, for example, as shown inFIG. 18. Thus, as shown at 110, the method 100 may then include infusingthe root inserts 46 and the spacers 52 between the inner and outerlayers 40, 42, e.g. via a resin. More specifically, in certainembodiments, the method 100 may include infusing the root inserts 46 andthe spacers 52 between the inner and outer layers 40, 42 via vacuuminfusion, resin transfer molding (RTM), light resin transfer molding(RTM), vacuum assisted resin transfer molding (VARTM), or similar.

In alternative embodiments, where the inner and outer layers 40, 42 andthe root inserts 46 are constructed of thermoplastic materials, themethod 100 may also include welding the thermoplastic inserts 46 betweenthe inner and outer layers 40, 42 (rather than including or bonding theinserts 46 between the inner and outer layers 40, 42). As such, thethermoplastic inserts 46 may be reheated, removed, and replaced in theevent of damage and/or manufacturing defects. More specifically, incertain embodiments, the method 100 may include heating the metalbushing 48 of the inserts 46 such that the surrounding thermoplasticmaterial is heated. Thus, the heated thermoplastic material can bewelded to surrounding thermoplastic mating surfaces, e.g. the inner andouter layers 40, 42. In additional embodiments, pressure may also beapplied from the root end of the metal bushing 48 to ensure a suitableweld bond. Accordingly, in further embodiments, a similar process may beused to remove an existing insert 46, i.e. by applying heat to the metalbushing 48 while pulling on the insert 46 to be removed.

The process for infusing, bonding, or welding the inserts 46 between theinner and outer layers 40, 42 can then be repeated for each blade half(if necessary). Further, the blade halves (where first and second shellmolds are used) are allowed to cure for a predetermined time period.Once cured, the removable flange 70 may be removed and reused tomanufacture additional root assemblies 30. In addition, the blade halves(if applicable) may be bonded together, e.g. with an adhesive, to formthe root assembly 30. The adhesive is then allowed to cure to a statesuitable for ejecting the root assembly 30 from the shell molds. Theroot assembly 30 may then be ejected from the shell mold 66 and locatedto an area for finishing.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A root assembly for a rotor blade of a windturbine, comprising: a blade root section comprising an inner sidewallsurface and an outer sidewall surface separated by a radial gap, theblade root section constructed of a first composite material, the firstcomposite material comprising a thermoplastic material; a plurality ofroot inserts spaced circumferentially within the radial gap, each of theroot inserts comprising at least one bushing cured within and surroundedby a second composite material formed primarily of a thermoset material,each of the bushings configured to receive a root bolt, the root boltsconfigured to secure the root assembly to a hub of the wind turbine;and, a plurality of spacers configured between one or more of the rootinserts, each of the spacers being constructed of a pre-consolidatedcomposite material.
 2. The root assembly of claim 1, wherein thethermoplastic material comprises at least one of polyvinyl chlorides(PVC), polyvinylidene chlorides, polyvinyl acetates, polypropylenes,polyethylenes, polystyrenes, polyurethanes, polyphenyl sulfide,polybutylene terephthalate (PBT), polyamides, polymethyl methacrylate(PMMA),glycolised polyethylene terephthalate (PET-G), or polyethyleneterephthalate (PET).
 3. The root assembly of claim 1, wherein thethermoset material comprises at least one of polyester, ester, epoxy,polyurethane, melamine formaldehyde, or urea formaldehyde.
 4. The rootassembly of claim 1, wherein the plurality of spacers are constructed,at least in part, of a thermoplastic material or a thermoset material.5. The root assembly of claim 1, wherein at least one of the thermosetmaterial or the thermoplastic material is reinforced with one or morefibers.
 6. The root assembly of claim 5, wherein the one or more fiberscomprise at least one of carbon fibers, carbon rovings, glass fibers, orglass rovings.
 7. The root assembly of claim 1, further comprising abonding agent configured within the radial gap, the bonding agentcomprising chopped fiber mat (CFM), a biaxially-stretched plastic film,or a three-dimensional glass fabric.
 8. A root assembly for a rotorblade of a wind turbine, comprising: a blade root section comprising aninner sidewall surface and an outer sidewall surface, the inner andouter sidewall surfaces being separated by a radial gap, the blade rootsection constructed, at least in part, of a first thermoplastic resin; aplurality of root inserts spaced circumferentially within the radialgap, each of the root inserts comprising at least one bushing curedwithin and surrounded primarily by a second thermoplastic resin, each ofthe bushings configured to receive a root bolt, the root boltsconfigured to secure the root assembly to a hub of the wind turbine, thefirst and second thermoplastic resins being different; and, a pluralityof spacers configured between one or more of the root inserts, each ofthe spacers being constructed of a pre-consolidated composite material.9. The root assembly of claim 8, wherein at least one of the firstthermoplastic resin or the second thermoplastic resin is reinforced withone or more fibers, wherein the one or more fibers comprise at least oneof carbon fibers or rovings or glass fibers or rovings.
 10. A rootassembly for a rotor blade of a wind turbine, comprising: a blade rootsection comprising an inner sidewall surface and an outer sidewallsurface, the inner and outer sidewall surfaces being separated by aradial gap, the blade root section constructed of a thermoset material;a plurality of root inserts spaced circumferentially within the radialgap, each of the root inserts comprising at least one bushing solidifiedwithin and surrounded primarily by a thermoplastic material, each of thebushings configured to receive a root bolt, the root bolts configured tosecure the root assembly to a hub of the wind turbine; and, a pluralityof spacers configured between one or more of the root inserts, each ofthe spacers being constructed of a pre-consolidated composite material.11. The root assembly of claim 10, wherein the thermoplastic materialcomprises at least one of polyvinyl chlorides (PVC), polyvinylidenechlorides, polyvinyl acetates, polypropylenes, polyethylenes,polystyrenes, polyurethanes, polyphenyl sulfide, polybutyleneterephthalate (PBT), polyamides, polymethyl methacrylate (PMMA),glycolised polyethylene terephthalate (PET-G), or polyethyleneterephthalate PET).
 12. The root assembly of claim 10, wherein thethermoset material comprises at least one of polyester, ester, epoxy,polyurethane, melamine formaldehyde, or urea formaldehyde.
 13. The rootassembly of claim 10, wherein the plurality of spacers are constructed,at least in part, of a thermoplastic material or a thermoset material.14. The root assembly of claim 10, wherein at least one of the thermosetmaterial or the thermoplastic material is reinforced with one or morefibers.
 15. The root assembly of claim 14, wherein the one or morefibers comprise at least one of carbon fibers, carbon rovings, glassfibers, or glass rovings.
 16. The root assembly of claim 10, furthercomprising a bonding agent configured within the radial gap, the bondingagent comprising chopped fiber mat (CFM), a biaxially-stretched plasticfilm, or a three-dimensional glass fabric.